JUKI LK-1900AN Engineer's Manual page 111

Trouble
From the previous page
3. Stitch Skipping
Cause (1)
2-4) Needle coming in contact
with the moving knife
2-5) Needle coming in contact
with the wiper
2-6) Needle is bent.
2-7) Needle is too thin.
3-1) Too much clearance between
the needle and the inner hook
3-2) Inadequate timing adjust-
ment for the needle and
the inner hook
3-3) Inadequate clearance
between the shuttle driver
and the needle
3-4) Material to be sewn is not
properly stretched.
3-5) Needle is bent or blunt.
3-6) Loop of the needle thread
falls down.
Cause (2)
6-A) The needle thread tension is too high.
6-B) The presser treads on the
needle thread at the beginning of
sewing and the wiper is caught.
4-A) Too much clearance between the
work clamp foot and sewing object
6-A) Feed timing is too fast.
Check and corrective measures
Adjust the moving knife position.
Adjust the work clamp foot (feed bracket)
position.
Adjust the wiper position.
Adjust the tension to a proper level.
Increase the crosswise clearance between
the wiper and the needle. (23 to 25 mm)
Change the needle No. to the suitable one
to the material.
Adjust the clearance between needle and
inner hook.
Adjust timing for the needle and the inner
hook.
Adjust the clearance between needle and
shuttle driver.
Adjust the work clamp foot height.
Remove the slackness of the sewing object.
Replace the needle.
Attach the needle with the long groove orient-
ing slightly to the right. (Approximately 20°)
Change the feed timing by the use of the
memory switch.